Drying and incineration of moist materials



Feb. 14, 1939. G. E. CONNOLLY DRYING AND INJINERATION 0F MOIST MATERIALS2 Sheets-sheaf 1 Filed Oct. 5, 1936 TIIIIIHHHHHHU llllllllR INVENTORkorgefi Cbmwlly BY Z 5. .4; V 4414/ ATTORNEY-5 Feb. 14, 1939,

G. E. CONNOLLY DRYING AND INCINERATION OF MOISTMATERIALS Filed Oct. 5,1936 2 Sheets-Sheet 2 INVENTOR [/eorgefi flannally BY 4424/ W 6ATTCRNEY5 Patented Feb. 14, 1939 UNITED STATES PATENT. OFFICE DRYING ANDINCINERATION OF MOIST MATERIALS Application October 5,

V 12 Claims.

This invention relates to the drying and burning of moist material andis more particularly adapted for the drying and incineration of wastematerial such as sewage sludge. The invention embodies variousimprovements and modifications of the method and apparatus of the patentto Dudley Baird and Robert W. Rowen, No. 2,015,050, granted September1'7, 1935.

Important features of this invention involve methods and. apparatuswhereby waste material .may be thoroughly incinerated and. the evolvedgases and vapor efficiently and thoroughly treated to eliminate noxiousodor. The invention also if desired may embody arrangements wherebydesired quantities of the waste material may be efliciently driedwithout burning the same, such quantities of the material then beingwithdrawn from the apparatus for use as fertilizer, while any remainingor excess portions of the material may be incinerated and the heatresulting from such incinerationmay be utilized to effect the dryingoperation, or to aid in effecting the same.

Various further and more specific objects, features and advantages willclearly'appear from the detailed description given below taken inconnection with the accompanying drawings which form a part of thisspecification and illustrate merely by way of example preferred forms ofthe apparatus of the invention.

The invention consists in such novel features, arrangements andcombinations of parts as .may be shown and described in connection withthe apparatus herein disclosed.

In the drawings,

Fig. 1 illustrates somewhat diagrammatically a preferred embodiment ofthe invention;

Fig. 2 similarly illustrates another desirable embodiment of theinvention; and

Fig. 3 illustrates a portion of apparatus such as shown in Fig. 1, butmodified in several respects.

Referring to Fig. 1, the apparatus there shown ,may comprise a furnace10 having a plurality of superposed hearths as at H, mounted within theupper portion of the furnace wherein the operation of burning orincinerating the material is preferably conducted, and also a pluralityof superposed hearths as at l2 mounted within the lower portion of thefurnace, wherein the operation of drying the material is carried out.

Except for the features hereinafter described in further detail, thefurnace may be of the same general type of construction as thatdisclosed in t the above mentioned Patent'No. 2,015,050, a. plu- 1936,Serial No. 103,970

rality of rabble arms as at 13 being provided at each hearth,'theserabble arms each being in turn provided with teeth as at 13' whereby thematerial will be distributed over each hearth as a relatively thin layerand will be periodically rabbled andgradually advanced over each hearthand through drop holes to the hearth below. However, one of the hearths,for example hearth M, at the mid portion of the furnace, may be formedwithout the usual drop holes whereby the furnace will be substantiallydivided into an upper incinerating portion and a lower drying portionfor purposes hereinafter explained.

The rabble arms may be mounted upon a rotatable central shaft as 'at 15and the rabble arms. and shaft may be provided with internal coolingconduits as in the above mentioned Patent No, 2,015,050. In theparticular construction shown, cooling air may be admitted as through anopening H5 at the base of, the shaft structure and withdrawn as by ablower I! mounted at the top of the shaft structure, the blower I! beingconnected to a conduit I8, which will thus carry a supply of airsomewhat preheated because of its passage through the conduits of therabbling structure.

The material to be treated may comprise for example, sewage sludgefilter cake or sewage sludge of other form, which has preferably been sotreated as to eliminate a considerable portion of the water content,as'for example by any wellknown mechanical dehydrating process. Or thematerial may comprise'for example, ground garbage or garbage mixed withsewage sludge filter,

cake or other waste material, and should preferably have a water contentin the neighborhood of 75% or less, although material having asubstantially higher water content may also be treated in the apparatus.

The material to be treated may be conducted as by a conveyor [9 to ahopper 20, thence through'a suitable furnace inlet feeding device as at2|, which will preferably substantially continuously permit the materialto be fed into the furnace but without any substantial escape of gasesor vapor at this point. From the device 2| the material may be fedthrough a conduit 22 on to the upper drying hearth 12. The material isthen periodically rabbled and gradually advanced over each of thedrying. hearths and from hearth to hearth down through the dryingportion of the furnace to an outlet as at 23. This drying may proceed inthe presence of counter current streams of preheated air, which may besupplied from a conduit 24 as hereinafter explained. If necessary, thetemperatures within this portion of the furnace may be increased. as bythe use of one or more gas or oil burners as indicated at 25. However,the temperatures in this portion of the furnace are preferably keptwithin a range such that there will be no burning or scorching of thematerial on the lower hearths, although the temperatures are madesuflicient to rapidly and thoroughly dry the material being treated,while due to the rabbling action, the material may become graduallybroken into finer and finer pieces as it becomes more and more dry andless adhering.

From the outlet 23 the dried material may be conducted through a chute23a to the base of a conveyor 26, thence to the top of the conveyor anddown through a chute 26a to a furnace in- .let feeding device 21, whichmay be similar to the device 2| above referred to. From the feedingdevice 21 the dried material may fall on to the top incinerating hearthl I. Here the rabbling means'serves to periodically agitate andgradually advance the material over each of the burning hearths and fromhearth to hearth down through the upperor incinerating portion of thefurnace, and to an ash chute as at 28 having its intake end at hearth l4and its outlet connected to an ash bin as at '29. Suitable temperaturesmay be secured within the incineration portion of the furnace as by theuse of one or'more oil or .gas burners as. indicated'at 30, provided ifdesired with a supply of preheated air for supporting combustion, thisair supply being furnished through conduit 3! in a manner hereinafterexplained. An additional supply of preheated air may also be introducedfor example, at one of the lower burning hearths through conduit 32.Also vapor'evolved from the drying material in the drying portion of thefurnace, together with some warm air, may be conducted through gas portsas at 33 from the space above the upper drying hearth into'the spaceabove the lower burning hearth. The incineration action within the upperportion of the furnace'may therefore take place in the presence ofcounter current streams of preheated air, together with gaseous productsof combustion and vapor evolved from the drying and burning material.These counter current streams may finally be drawn off as through anexit opening 34 to conduit 35 connected to the upper portion of thefurnace. Thus it will be noted that all of the gaseous products ofcombustion and vapor evolved from the drying and burning material, maybe drawn off through substantially the hottest part of the furnace andhence may be readily subjected before their exit to temperatures in theneighborhood of 1l00 to 1500 R, which are ordinarily sufiicient tosafely destroy the noxious odors of the gases and vapor.

From the conduit 35 the gases and vapor may be drawn down'through arecuperator 36 as by a suction fan 31 and finally conducted to a stack38 or other means for disposal thereof.

The air within conduit l8 which has been somewhat preheated by passagethrough the rabbling structure, may be passed through the recuperator 36in heat exchanging relationship with the hot exit gases and vapor, sothat such air thus be-' comes further preheated before it leaves thereouperator, as through a conduit 39. From conduit'39, desired portionsof this preheated air maybe conducted into the furnace through conduits24, 3| and 32, the amount admitted through each of these conduits beingcontrolled as by the adjustment of dampers as indicated.

While several burning hearths and several drying hearths are indicatedin the particular example shown, it will be understood that under somecircumstances if desired, the drying may be conducted on a single dryinghearth made of sufficient area to accommodate the quantity .of materialbeing treated, and similarly the incineration may be conducted on one ormore incineration hearths. The conveyor 26 and the various chutes andconduits for conducting the material into and out of the furnace arepreferably suitably enclosed so as to prevent the escape of anyodoriferous gases, vapor or dust.

In cases where it may be desired to use some of the dried material asfertilizer, fuel, or for other purposes, then a portion or at times allof the dried material at the outlet 23 may be allowed to fall through achute as at 40 on to a conveyor as at 4|. The proportion of the driedmaterial thus withdrawn from the apparatus may be adjusted by adjustmentof a gate member as at 42. The material which is not withdrawn at thispoint may be conveyed to the incinerating portion of the furnace andburned in the manner above explained,

In case the supplies of waste material at times embody an abnormalpercentage of moisture, it may be desirable to treat a substantial partof the material more than once in the drying portion of the furnace.Orin some cases it may be possible to reduce the number or area of thedrying hearths considerably by recirculating part of the partially driedmaterial through the drying hearth spaces. This may be done byconducting a part of the dried material from chute 26a through. a chute43 into hopper 20. The pro-portion of the partially dried material thusrecirculated may be varied or regulated by adjusting a gate member as.at M at the entrance to chute 43. Since the drying and burningoperations are effectively isolated against merging with each other,this recirculation of the dried material may be efficiently carried outwithout danger of introducing ignited material into the wet sludge withconsequent lumping and irregular drying and the discharge of obnoxiousgases and steam, as would occur if such recirculation were attemptedwith the prior multiple hearth apparatus.

With the above described form of the apparatus it will be noted that thegaseous products of combustion and vapor evolved from the burning anddrying material are substantially free to follow their natural upwarddirection of flow through the furnace and yet the arrangement is such asto permit all of the evolved vapor and gases to be drawn off throughsubstantially the hottest portion of the furnace at the incinerationhearths whereby noxious odors from the evolved gases may be efficientlyand thoroughly eliminated.

Also since the drying portion of the furnace is eflieientlytransferiheatto'a supply .of intake air for supportingefiicient combustion within theburning portion .of the furnace.

Where the drying hearths .are within the top of the furnace, .withtheburning hearths below, in accordance with the practice heretofore, thereis a marked tendency at times for the high temperature flame to progressupwardly from the burning hearths along the scattering stream offalling. dried sludge, into the. drying hearths. Thus it will ,beapparent that the line of division between the drying and burninghearths cannot'be so sharplydefinedas to permit withdrawal .ofthoroughlydried sludge for use as fertilizer, etc., with the arrangementsheretofore allailable, without at times, also withdrawing smoldering,.charred ,or odoriferous sludge and gases. However, with the abovedescribed arrangement having the drying hearths at the bottom and theburning hearths at the top, a definite predetermined separation ispossible between the drying and burning hearths, with no substantialpossibility for the flames of theburning gas or for hot coals from theburning hearths to enter and .start combustion in the drying hearths.This will be apparent when it is noted that the first drying. hearthcarrying the wettest and least. combustible material, is the one whichis located nearest the cooler burning hearth carrying little but ash.Thus the particular burning hearth which is substantially free of flamesand carries few if any live coals of burning material, is closest to thedrying hearth which is carrying the material in a condition where it ismost difiicult to ignite. These facts, together with the above describedarrangements of gas passages, make possible a substantial isolation ofthe burning hearths againstpassage of burning material or flames intothe drying hearths. Although' the arrangement permits the drying andburning operations to :be thus substantially isolated against mergingwith each other, yet the structure is such. as to permit all of thehearths to be enclosed within a single cylindrical furnace wallproviding a compact structure conserving of heat and space, In fact, therequired floor space is not increased over the requirements of thepreviously known apparatus, which cannot fulfill several of the abovedescribed functions of the present invention.

In Fig. 2 a somewhat similar embodiment of the invention isillustrated,like parts being indicated by the same reference numerals. However, inFig. 2 the arrangement is such that the streams of gases, vapor and airwithin the furnace are passed along the path of travel of the drying andburning material, i. e. downwardly through the furnace; That is, air inconduit l8 preheated by passage through the rabbling structure, may befurther preheated in a recuperator 50 and then conducted by conduit 5!to a furnace air intake opening 52 located at the upper part of thefurnace. If desired, a part of this preheated air may be conducted asthrough conduits 53 and 54 to oil or gas burners as indicated at 55. Theamount of air thus conveyed to each of the burners and the amountconveyed directly into the upper part of the furnace, maybe regulated byadjusting the various dampers as shown. Within the furnace the gaseousproducts of combustion evolved from the burning material at the upperhearths, together with any excess air 7 not used. for combustionpurposes, may pass downwardly through the gas ports 33 into the r i gportio of the furnace and thence downwardly through the. drying Portionso that the ases, evolvedvaporandremaining air finally re passed outthrough an exit opening as at '56 at the bottom .of the furnace. Fromthis point the gas, vapor and air mixture maybe drawn through a conduit:51 and recuperator 5,0 by asuction fan as .at '58 andjdischarged to astack as at 59.

It is apparent that the arrangement of Fig. 2

embodies many of the same advantages as the apparatus of Fig. 1. ,Inaddition, the apparatus of Fig. v2 permits the drying action in thelower part of the furnace to .be largely effected by the heat of theevolved gaseous products of combustion coming from the upper part of thefurnace with substantially a minimum of air. Accordingly, while thedrying action will be eificiently promoted in the drying portion of thefurnace, the absence of much air will prevent any danger of SQQrching orburning the drying material. Thus the danger of any substantial noxiousodors being evolved at the drying hearths will be eliminated and any ofthe dried product which is withdrawn at the bottom of the furnace willbe free .of burned, scorched, odoriferous material or ash. The hearth l4having no material drop holes, will prevent glowing clinkers and ashfrom falling into the dry ng material, so that danger of igniting thedrying material will be eliminated, at the same time keeping the dryingmaterial free of ash in case it is desired to use the same forfertilizer without such ash. However, if the material being treated isof such a nature that the presence of a relatively small amount of ashin the dried fertilizer product is not objec tionable, then the ash fromthe burning hearths may be conducted from chute 28 into one of thedrying hearths.

While we have illustrated the apparatus with fuel burners formaintaining the desired temperatures both in the drying and burningportions of the furnace, in some cases especially where the materialbeing treated does not have an unusually large moisture content, theprocess may be carried on without the use of extraneous fuel in view ofthe recovery of heat. by the use of the recuperator. Additional heat mayalso be recovered to avoid the use of extraneous fuel by usingrecuperator arrangements following the principles of those disclosed inthe copending application of Henry J. Hartley and Dudley Baird, Ser. No.95,950, filed August 14, 1936.

In some cases instead of using oil or gas burners to heat the furnace,or instead of relying wholly on such burners to provide any extraneousfuel necessary, it may be found desirable to provide fuel in finelydivided solid form. In that event a finely divided fuel such for exampleas powdered coal, sawdust or other fuel which may be cheaply available,may be mixed with the waste material and carried into the apparatus withthe waste material on conveyor Hi. However, in the event that it isdesired to use a portion of the dried waste material as fertilizer, thenthe finely divided fuel material may be mixed with the remaining wastematerial after the latter has become dried. That is, for example,powdered coal or other finely divided fuel may be supplied as from ahopper 60 through an adjustable gate 6| into the chute or conduit 26a.The introduction of the finely divided fuel at this point not only hasthe advantage of permitting portions of the dried material to bewithdrawn from the apparatus for use as fertilizer free of fuel or fuelash, but also the fuel may thus be; mo,re uniformly and thoroughly mixedwith the waste material after the latter has become quite thoroughlydried'and finely divided. The introduction of the fuel at this pointalso avoids any possibility of the distillation of noxious gases fromthe fuel in the drying section of the furnace and eliminates any dangerof unintended combustion occurring in the drying section. Furthermore;the mixing of the fuel with the dried waste material just beforeincineration, substantially avoids any possibility that the fuel willsmolder and produce objectionable smoke, as might occur where the fuelis mixed with the Wet sludge.

.In Fig. 3 a further modification of the apparatus of Fig. 1 isillustrated. With this arrangement, preheated air may be supplied to theupper sections of the furnace through conduits 52 and 63, correspondingto conduits 3| and 32 of Fig. 1. However, instead of introducingpreheated air at the bottom of the drying section of the furnace as inFig. 1, an arrangement is shown in Fig. 3 for introducing preheated 'airby a conduit 64 into the top of the drying portion of the furnace,whereby such air passes downwardly from hearth to hearth through thedrying section of the furnace. The air then, together with vapor evolvedfrom the drying material, may pass out from the bottom of the furnacethrough one or more conduits 65, and into the burning section of thefurnace. The arrangement of Fig. 3is particularly desirable incaseswhere relatively dry waste material is being treated, in that thepreheated air is introduced at an upper drying hearth where the materialis more moist, and hence less likely to be scorched or burned by thepreheated air. 33; the time the air arrives at the lower drying hearthswhere the material is quite dry, the temperature ofthe air will besufiiciently decreased so that combustion is also avoided at this point,notwithstanding the dryness of the material.

.While the invention has been described in detail with respect toparticular preferred examples, it will be understood by those skilled inthe art after understanding the invention, that various changes andfurther modifications may be made without departing from the spirit andscope of the invention, and it is intended therefore in the appendedclaims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

w 1. Apparatus for drying and incinerating waste materials, comprising afurnace having a plurality of superposed hearths all surrounded by afurnace wall and including one or more lower hearths for drying thematerial and one or more upper hearths for burning the material, saiddrying hearths being substantially isolated against passage of solidmaterial thereto from said burning hearths, means for introducing thematerial onto said drying hearth or hearths and for rabbling thematerial thereover while the material is being dried, means forwithdrawing a portion of the dried material from the apparatus, andmeans for conveying the remainder of the dried material to said burninghearth or hearths and for rabbling such remaining material over saidburning hearth or hearths.

2. A furnace for drying and burning moist material, comprising aplurality of superposed hearthsincludingone or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, means for introducing the material onto said drying hearth orhearths and for rabbling the material thereover in the presence of acountercurrent stream of heated air, means for conveying the materialafter passage over said drying hearth or hearths to said burning hearthor hearths and for rabbling the material over the latter, means forconducting said stream together with vapor evolved from the dryingmaterial into contact with the material on said burning hearth orhearths and for then conducting said stream together with gaseousproducts of combustion evolved from the burning material countercurrentto the burning material over the burning hearth or hearths, said dryinghearths being substantially isolated against passage of solid materialthereto from said burning hearths, and an exit opening above an upperburning hearth whereby said gases and vapor may be withdrawn from thefurnace through a high temperature burning zone for the destruction ofnoxious odor of such gases and vapor.

3. A furnace for drying and burning moist ma terial, comprising aplurality of superposed hearths including one or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, means for introducing the material onto said drying hearth orhearths and for rabbling the material thereover, means for thenconveying the material to said burning hearth or hearths and forrabbling the material thereover, means for causing a stream of airtogether with vapor and gases evolved from the material to passcountercurrent to the movement of the material over said drying hearthor hearths and then over said burning hearth or hearths, means includingan exit opening at an upper burning hearth for withdrawing saidcountercurrent stream from the furnace through a high temperatureburning zone thereof, and. a heat exchanging device and connectionswhereby heat of said withdrawn stream may be transferred to a supply ofintake air for the furnace.

4. A furnace for drying and burning moist material, comprising aplurality of superposed hearths including one or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, means for introducing the material onto said drying hearth orhearths and for rabbling the material therea over, means for thenconveying the material to said burning hearth or hearths and forrabbling thematerial thereover, means for substantially isolating saidburning hearths against passage of burning material therefrom to saiddrying hearths, and means for causing a stream of hot air to pass overthe material on said burning hearth or hearths and for then causingremaining air of said stream together with hot gases evolved from theburning material, to pass over the material on said drying hearth orhearths whereby the'material is dried in an atmosphere unfavorable forcombustion.

5. A furnace for drying and burning moist material, comprising aplurality of superposed hearths including one or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, an ash outlet from the furnace located substantially at apoint between said upper and lower hearths, means for introducing thematerial onto said drying hearth or hearths and for rabbling thematerial thereover, means for then conveying the material to saidburning hearth or hearths and for rabbling the material thereover and tosaid ash outlet, means for causing a stream of hot air to pass over thematerial of said drying hearth or hearths and for then causing saidstream together with vapor evolved from the drying material, to passover the material on said burning hearth or hearths, and means includingan exit opening at a burning hearth for withdrawing said stream togetherwith said vapor and gases evolved from the burning material, from thefurnace through a high temperature burning zone.

6. A furnace for drying and burning moist material, comprising aplurality of superposed hearths including one or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, means for introducing the material onto said drying hearth orhearths and for rabbling the material thereover, means for thenconveying the material to said burning hearth or hearths and forrabbling the material thereover, means for substantially isolating saidburning hearths against passage of burning material therefrom to saiddrying hearths, and means for causing a stream of hot air to pass overthe material on said burning hearth or hearths and along the path oftravel of the material thereon, and for then causing remaining air ofsaid stream together with hot gases evolved from the burning material,to

pass over the material on said drying hearth or hearths, along the pathof travel of the drying material.

7. A furnace for drying and burning moist material, comprising aplurality of superposed hearths including one or more lower hearths fordrying the material and one or more upper hearths for burning thematerial, means for introducing the material onto said drying hearth orhearths and for rabbling the material thereover, means for thenconveying the material to said burning hearth or hearths and for rab-'bling the material thereover, means for substantially isolating saidburning hearths against passage of burning material therefrom to saiddrying hearths, means for causing a stream of hot air to pass over thematerial on said burning hearth or hearths and for then causingremaining air of said stream together with hot gases evolved from theburning material, to pass over the material on said drying hearth orhearths whereby the material is dried in an atmosphere unfavorable forcombustion, and a heat exchanging device and connections for thenconducting said gases together with vapor evolved from the dryingmaterial through said device in heat exchanging relationship with asupply of intake air for said burning hearth or hearths, whereby saidintake air is preheated.

8. A furnace for drying and burning moist material, comprising aplurality of superposed burning hearths within the upper part of thefurnace, a plurality of superposed drying hearths within the lower partof the furnace isolated against the passage of solid material theretofrom said.

burning hearths, means for rabbling the material over said drying andburning hearths respectively, and means for conveying dried materialfrom said drying hearths onto said burning hearths.

9. A furnace for drying and burning moist material, comprising aplurality of superposed burning hearths within the upper part of thefurnace, a plurality of superposed drying hearths within the lower partof the furnace isolated against the passage of solid and burningmaterial thereto from said burning hearths, means for rabbling thematerial over said drying and burning hearths respectively, and meansfor conveying dried material from said drying hearths onto said burninghearths, the furnace being provided with a gas passage or passagesinterconnecting said upper and lower parts, and also with hearth ports,permitting a stream-of gases to communicate with spaces over both thedrying and burning hearths,

10. Apparatus for drying and burning sewage material, comprising afurnace having a plurality of superposed hearths for drying the materialand also a plurality of superposed hearths for burning the materiallocated above said drying hearths and enclosed in a unitary structuretherewith, means for introducing the material onto an upper dryinghearth, means for then rabbling the material over the drying hearths insuccession, means for returning a portion of the material from a lowerdrying hearth to an upper drying hearth and for depositing anotherportion of the material from a lower drying hearth onto an upper burninghearth, and means for then rabbling the latter portion over the burninghearths in succession.

11. Apparatus for drying and incinerating sewage sludge material,comprising a plurality of superposed hearths enclosed within a furnacewall and including one or more lower hearths for drying the material andone or more upper hearths for burning the material, means forintroducing the material onto said drying hearth or hearths and forrabbling the material thereover whereby the material becomes dried andfinely divided, means for then conveying the dried material to saidburning hearth or hearths, means for mixing finely divided solid fuelwith said finely divided dried material prior to the introduction of thelatter into said burning hearth or hearths, and means for agitating andgradually advancing the mixture over said burning hearth or hearths.

12. Apparatus for drying and incinerating waste materials, comprising afurnace having a plurality of superposed hearths including one or morelower hearths for drying the material and one or more upper hearths forburning the material, said drying hearths being substantially isolatedagainst passage of solid material thereto from said burning hearths,means for introducing the material onto said drying hearth or hearthsand for rabbling the material thereover while the material is beingdried, means for withdrawing a portion of the dried material from theapparatus, and means for conveying the remainder of the dried materialto said burning hearth or hearths and for rabbling such remain- GEORGEE. CONNOLLY.

